It is common in practice to exploit stretch film for unitizing goods. The application of such film is usually automated, semi-automated or via the hand-wrapping technique. However, due to sharp corners for example on a pallet or in homogeneities in the film, tearing may occur during application which can lead to catastrophic failure. Such events during wrapping interrupt the packaging procedure requiring additional time and effort for the end-user. In order to minimize failure during wrapping, thicker films are commonly selected. Therefore, the packaging cost and tension necessary to stretch the film are considerably increased.
It is expected that reinforcement of stretch film will hinder the tear propagation during wrapping. In an attempt to compensate film thickness increase and degree of reinforcement WO 2005/021240 A1 describes a film for packaging wherein a section transversal to the longitudinal direction is provided with areas of a greater thickness alternated with areas having a lower thickness. In this embodiment, the thicker areas of said film act as reinforcement. However, the use of the same resin for both film and reinforcement area limits the reinforcing capabilities of said film.
WO 2011/026954 A2 describes a reinforced stretch film wherein a plurality of reinforcing fiber elements protrudes on a base film. The average thickness of the protrusions is always more than the average thickness of the base film. However, the domain of material mixture required at the location where the extruded fiber elements are provided on the base film reduces the thickness of the pure base film material beneath. This latter limits some mechanical properties of said film especially when the base film thickness is very low.
WO 2006/016393 A1 presents a film of extensible packaging material which has longitudinal reinforcing side strips coupled onto a stretch film. Although the edges of said film are reinforced, the rest of the film is prone to tear propagation. The same issue applies to WO 2009/049804 A1.
U.S. Pat. No. 5,013,595 discusses the strengthening of a stretch film with at least an auxiliary band. Said auxiliary band is preferably single. EP 1 584 574 A2 presents a stretch film reinforced with at least one reinforcement strip having a width up to 10% the width of the film. Therein, at least one strip is preferably waved along the longitudinal direction.
WO 03/013854 A1 describes a packaging film reinforced by a highly pre-stretched film of 7 μm to 20 μm thickness which is located on a base film of 14 μm to 35 μm thickness. The limited extensibility claimed for the reinforcement increases prominently the tension required to use the film while blocking rips generated during application.
WO 2011/026953 describes a reinforced tacky stretch film. The base film comprises a stretchable polymeric material having perforations covering at least 25% of the total area of the base film. The perforations are arranged in a series of columns. The film also comprises a multiplicity of strengthening elements fixed on the base film parallel to the longitudinal direction.
Films according to the prior art often have relatively wide reinforcing strips. In the case of stretch films reinforced with only a few strips, tearing is blocked by the strips but a significant proportion of the film between the strips becomes torn. The packaging thus becomes non-functional. When more of these reinforcing strips are placed on the base film to overcome this problem, the stretch film becomes heavier, stiffer, and more tension is required to apply the film. For machine application, the use of such reinforcement on the film may induce slippage of the reinforced film on the stretching rolls, thus less final pre-stretching ratio than expected is obtained. For manual stretching the situation may be worse as the worker will not be able to stretch adequately by hand the film during wrapping. In both of these cases, although a tear will be blocked at the strips, the packaging may not be approved due to increased packaging cost per pallet (i.e. more film/pallet) and/or to inferior goods unitization. Moreover, the hindering of the automated or manual cut at the end of the wrapping is expected now to be more pronounced. This may again be referred to as non-functional.
The object of present invention is to overcome the problems mentioned above, and provide a film wrapping procedure which is not interrupted by breakages such that the goods are adequately protected after utilization. The film should apply even distribution of force to the goods without crushing them. It should be noted that the film of the present invention is specifically used for wrapping of goods, i.e. it cannot be used as an adhesive tape and therefore does not have an adhesive layer.